Intracapsular accomodative implants

ABSTRACT

An accommodative intracapsular implant comprises a central optical part and at least two haptic arms ( 3, 4 ), the free ends ( 5, 6 ) of which are embodied to cooperate with parts of the equatorial zone of the capsular bag, wherein the optical part is formed by joining two elastically-deformable bodies, one body being formed as an envelope ( 1 ) and the other body being formed as a core ( 2 ).

The replacement of the natural crystalline lens by an artificialcrystalline lens (implant) is nowadays usually practiced, in particularon subjects reached of cataract.

The surgery more practiced consists in withdrawing the matter of thenatural crystalline lens contained in the capsular bag while preservingthe integrity of this bag (except to the central part of its anteriorwall) which then remains the receptacle of the implant located thereinto replace the withdrawn natural matter.

BACKGROUND OF THE INVENTION

There are now many implants. Most of them allow about recovering a farvision without accommodation possibility for a near vision.

Natural accommodation has made the subject of many studies with the aimto understand the phenomena which are involved to try to transpose themto the implants. The role of the capsular bag in the accommodation isextremely significant, in particular as an element of transmission tothe crystalline matter of the forces generated by the ciliary muscle inthe one or the other of its relaxed or contracted states, to which thecapsular bag is connected by the zonular fibers.

Most recent work to date on the accommodative intracapsular lensesshowed that the capsular bag and the crystalline matter are providedwith their own elasticity which give the natural crystalline lens amodifiable form depending on the balance of forces between the state oftension of the zonular fibers, the elasticity of the capsular bag andthe elasticity of the crystalline matter.

The loss of the accommodative capacity seems to be the result of analteration of the module of elasticity of the crystalline matter in thecourse of the time, which opposes an increasingly large resistance tothe force of the bag for finally solidifying in an invariable state(regarding the forces brought into play) close to its shape for the farvision. This is the phenomenon of presbyopia.

OBJECT OF THE INVENTION

One of the objects of the invention is to propose an accommodativeintracapsular implant which reproduces the natural mechanisms broughtinto play at the time of the accommodation.

BRIEF DESCRIPTION OF THE INVENTION

To this end the invention relates to an accommodative implant includinga central optical part and at least two haptic arms whose loose ends areformed to co-operate with portions of the equatorial zone of thecapsular bag, characterized in that the optical part is formed by twobodies elastically deformable joined together, one shaped as an envelopeand the other in the shape of core, said envelope having an externalsurface with a convex anterior face which has, when the envelope isempty, a first radius of curvature and when the core is housed in theenvelope, a second radius of curvature different from the first radiusof curvature.

It is thus reproduced, in the optical part of the implant an elasticstructure in which two fields of antagonistic forces reign which give tothe structure a determined shape when the forces are balanced. Adisturbance of this balance by the addition of external forces resultsin a change of the shape of the optical part, in particular of the curveof its anterior face and thus of its optical power. The external forcesare the ones transmitted to said composite optical part by the hapticparts which are themselves subjected to the change of the shape of theequatorial zone of the capsular bag. The implant accommodates primarilyby a shape change of the optical part (with also a displacement of thisone along the optical axis of the eye) contrary to all the knownimplants which accommodate only by displacement.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics of the invention will appear in the descriptiongiven hereafter as an example of one embodiment.

It will be referred to the annexed drawings in which:

FIG. 1 is a diametrical cross section of the envelope of the implantaccording to the invention,

FIG. 2 is a diametrical cross section of the core of the implantaccording to the invention,

FIG. 3 is a diametrical cross section of the implant according to theinvention, the envelope housing the core,

FIG. 4 is a diametrical cut of the implant in its configurationcorresponding in an accommodated state,

FIGS. 5 and 6 illustrate an alternative embodiment of FIGS. 1 and 2,

FIG. 7 is a partial top view of the implant according to the invention.

The implant includes two parts: an envelope 1 represented empty on FIG.1 and a core 2 represented in its free state on FIG. 2. The envelope 1forms a hull made of elastic material, provided with two radial arms 3and 4 equipped with end soles 5 and 6. This is the haptic part of theimplant which engages equatorial zones of the capsular bag of the eyewhich is not represented.

Interior volume V of hull 1 is identical to volume V of core 2. Thiscore 2 is carried out in an elastomer material, therefore elasticallydeformable so that when introduced into hull 2 this latter is inflatedby the core and the core is flattened by the hull, because the freeshape of the core 2 is more convex than the shape of volume V of thehull. The final shape reached by the optical part of the implant (thatconstitutes volume V of the hull filled with the core 2) is representedon FIG. 3.

Interior volume of the hull may be slightly greater than the one of thecore made of elastomeric material in as much as this volume in excesshas no significant influence on the mutual action of the hull and thecore when assembled. The location of the core into the hull is made byany appropriate means: injection through an equatorial slit of the hull,junction of two half hulls around the core . . . .

In this shape, the radius of curvature R2 of the anterior face 1 a ofhull 1 is different from this same radius R1 when the hull is empty.Here the R2 radius is smaller than the radius R1. The shape reached onFIG. 3 is the result of the balance of two fields of antagonistic forcesborn from the elastic compression of core 2 by hull 1 and from elasticexpansion of hull 1 by core 2.

By causing an alteration of this balance by an external field of forcesF (see FIG. 4) one modifies the balance, therefore the shape, of theoptical part of the implant, therefore the radius of curvature R3 of itsanterior face 1 a is modified. The optical power of the composite lens1, 2 is thus modified.

In the case of FIG. 4, the field of forces F results from the action ofthe capsular bag on soles 5 and 6 when the zonular fibers are relaxedand that, by natural elasticity, the bag contracts radially. This is thestate of the implant for near vision, the radius R3 being smaller thanthe radius R2 which corresponds to the shape of the lens for a farvision.

Of course the posterior face 1 b of hull 1 has its radius of curvaturechanging as a result of the modification of the balance of the forces.It is possible, for example, by means of using various thicknesses ofthe hull wall 1, to influence such or such deformation, anterior orposterior, or even such type of deformation (spherical, conical . . . ).FIG. 7 shows slits 7 provided in the anterior wall of the hull 1 toillustrate means of adjustment of the ability of this hull to becomedeformed.

On FIGS. 5 and 6, the shown embodiment illustrates a hull 10 which,empty, has a volume V more convex than that of core 20 to be housed.This difference in shapes generates, like previously, fields of forces,the balance of which results in the intermediate shape of the corehoused in the hull.

Core 2, 20 can be made of a non elastic colloidal material (gel) housedin an envelope or an elastic pocket which confers to him its shape andits capacity with being elastically deformed.

1. An accommodative intracapsular implant comprising: a central opticalpart; and at least two haptic arms (3,4), free ends (5,6) of which areformed to cooperate with portions of equatorial zones of a capsular bag,wherein said optical part is formed by two bodies, elasticallydeformable and joined together, wherein: one body is shaped as anenvelope (I), having an interior volume (V) and with an envelope initialfree shape, and the other body is shaped as a core (2), having a volume(V) and a core initial free shape, the interior volume (V) of theenvelope (1) is identical to the volume (V) of the core (2), the coreinitial free shape is more convex than the envelope initial free shape,such that the core (2), when introduced into the envelope (I), isflattened by the envelope (1), the envelope (1) has an external surfacewith a convex anterior face (1 a) which has, when the envelope (1) isempty, a first radius of curvature (R1), and when the envelope (1)houses the core (2), a second radius of curvature (R2), said secondradius of curvature (R2) being smaller than said first radius ofcurvature (R1), and when the envelope (I) houses the core (2) and afield of forces (F) resulting from a radial contraction of the capsularbag is applied to the free ends (5, 6) of the haptic arms (3, 4), athird radius of curvature (R3), said third radius of curvature (R3)being smaller than said second radius of curvature (R2), thus resultingin a change of the optical power of the optical part.
 2. An implantaccording to claim 1, wherein the interior volume (V) of the envelope(1) is identical to the volume (V) of the core (2) with the envelopeinitial free shape being different from the core initial free shape,when the envelope (1) and the core (2) are in a free state with the corenot inserted into the envelope.
 3. An implant according to claim 1,wherein the core (2) is made of an elastomeric material defining theinitial free shape of the core.
 4. An implant according to claim 1,wherein the anterior wall of the envelope is provided with at least oneradial slit (7).
 5. An accommodative intracapsular implant comprising: acentral optical part; two haptic arms (3, 4)with respective free ends(5,6) for cooperation with portions of equatorial zones of a capsularbag, wherein said optical part is formed by two bodies, elasticallydeformable and joined together and one body is shaped as an envelope(I), having an interior volume (V) and an envelope initial free shape,and the other body is shaped as a core (2), having a volume (V) and ancore initial free shape, the interior volume (V) of the envelope (1) isgreater than the volume (V) of the core (2), the core initial free shapeis more convex than the shape of the volume (V) of the envelope (1),such that the core (2), when introduced into the envelope (I), isflattened by the envelope (1), the envelope (1) has an external surfacewith a convex anterior face (la) which has, when the envelope (1) isempty, a first radius of curvature (Ri), and when the envelope (1)houses the core (2), a second radius of curvature (R2), said secondradius of curvature (R2) being smaller than said first radius ofcurvature (R 1), when the envelope (1) houses the core (2) and a fieldof forces resulting from the radial contraction of the capsular bag isapplied to the free ends (5,6) of the haptic arms (3,4), a third radiusof curvature (R3), said third radius of curvature (R3) being smallerthan said second radius of curvature (R2), thus resulting in a change ofthe optical power of the optical part.
 6. An accommodative intracapsularimplant comprising: an elastically deformable envelope body having anempty interior volume and having an envelope body empty initial shapewith anterior face with an empty initial shape radius of curvature andhaving two haptic arms with respective free ends for cooperation withportions of equatorial zones of a capsular bag; and an elasticallydeformable core body having a non-inserted core body initial volume anda non-inserted core body initial shape that is more convex than saidenvelope body empty initial shape, said core body being inserted intosaid envelope body to form a central optical part having an equilibriumshape differing from said envelope body empty initial shape anddiffering from said non-inserted core body initial shape, said envelopebody exerting a pre-compression/tension on said core body to bias saidcore body toward a flatter shape than said core body initial shape andsaid core body exerting a pre-compression/tension on said envelope bodyto bias said envelope body toward a more convex shape than said envelopebody initial shape, said anterior face of said envelope body, in saidequilibrium shape, having an equilibrium shape radius of curvature thatis smaller than said empty initial shape radius of curvature, andwhereby upon a field of forces, resulting from the radial contraction ofthe capsular bag, being applied to said free ends, said forces at leastpartially counteracting or acting with said envelope body exerting apre-compression/tension on said core body and said forces at leastpartially counteracting or acting with said core body exerting apre-compression/tension on said envelope body to change from saidequilibrium shape to an applied force shape having an applied forceshape radius of curvature that is different from said empty initialshape radius of curvature, thus resulting in a change of the opticalpower of the optical part.
 7. An implant according to claim 6, whereinsaid empty interior volume of said envelope body is substantially thesame as said non-inserted core body initial volume.
 8. An implantaccording to claim 6, wherein said empty interior volume of saidenvelope body is larger than said non-inserted core body initial volume.9. An implant according to claim 6, wherein said anterior wall of theenvelope is provided with at least one radial slit.